1. Field of the Invention
The present invention relates to the improvements of a blood pressure measuring apparatus which measures a blood pressure value of a living subject such as a patient.
2. Related Art Statement
There is known an automatic blood pressure (BP) measuring apparatus which carries out BP measurements on a patient, accumulatively stores a measured BP value or values obtained in each BP measurement, and provides a graphic representation of the stored BP values arranged in the order of measurement. An example of the BP measuring apparatus is disclosed in Non-Examined Japanese Patent Application laid open under Publication No. 5(1993)-137698. The BP apparatus enables the patient to easily recognize the time change of the measured BP values and correctly judge whether he or she is in a healthy condition. When the patient feels tight in the chest, such a light attack may, however, be transient, so that the patient may fail to recognize that he or she possibly has a serious heart disease. Even if the patient may reach the recognition and consult a doctor, then the patient may no longer have any subjective symptom and may appear to the doctor to have no medical problem. In this case, the doctor may make a diagnosis based on insufficient examination data, e.g., BP values only. If the prior BP apparatus is used to obtain the BP values of the patient, however, the BP apparatus provides only the measured BP values of the patient, or only the time change of the measured BP values. With those data, the patient may suspect that he or she may have hypertension, but the patient cannot make a self-diagnosis, or the doctor cannot make a medical diagnosis, that he or she may have a heart disease. If the patient continues his or her life without receiving any medical treatments, he or she might be brought into a serious condition.
There is also known an automatic BP measuring apparatus which has a BP measuring device for automatically measuring a BP value or values of a living body, and a BP-value storing device for accumulatively storing the BP values measured by the BP measuring device from the living body. The BP measuring apparatus outputs the BP values accumulatively stored in the BP-value storing device, each time a new BP value or values of the subject is/are measured by the BP measuring device. Thus, the living body can easily recognize the time change of his or her BP values and effectively utilize the BP values for his or her health control. However, in the case where the BP values output from the BP apparatus do not fall within a normal BP range and care should be taken of the living body, just the marshalling of figures would give only a weak visual impression to the living body. Even if the living body may recognize his or her blood pressure abnormality, he or she is likely to forget it. While it is possible to output a pictorial image together with the BP values to give a stronger visual impression to the living body, it needs much time and effort to prepare the pictorial image or images. Moreover, in the case where a doctor gives a blood pressure-treating medicine to a patient after having made a diagnosis based on measured BP values, it may be somewhat cumbersome for the doctor to explain the directions for use of the medicine, the objects of administration of the same, and other necessary items.
Next, there is known an arm belt which is, either manually or using a winding device, wound around an upper arm of a living body or subject and which has an inflatable bag to which a pressurized air is supplied to press the arteries of the arm and measure a BP value or values of the subject. The supplying of the air to the bag is effected after the belt is wound around subject""s arm, and the measurement of BP values is carried out while the air pressure of the bag is changed. It is preferred that the belt be wound around the arm such that three fingers can be inserted between the skin of the arm and the inside surface of the belt. However, since the upper arm of the subject around which the arm belt is wound is easily deformable, a certain level of skill is needed for winding the belt wound the arm with a preferable pressing force and measuring a BP value or values of the subject with accuracy. Hence, there has been used a winding device which automatically winds an arm belt around an upper arm of a living subject. The automatic winding device has a cylindrical arm receiver in which the belt taking. a cylindrical shape is provided, and has a drive device such as a motor for tightening the belt. After the subject inserts his or her arm into the belt inside the receiver through one end of the receiver, the drive device is operated to tighten the belt and thereby reduce the inside diameter of the cylindrical belt. Thus, the arm belt is automatically wound around the subject""s upper arm. When a BP measurement is carried out using the automatic winding device, it is required that the arteries of the upper arm of the subject be uniformly pressed by the arm belt. To this end, generally, an elbow rest is provided outside the other end of the arm receiver, and the subject inserts his or her arm such that the elbow of the arm rests on the rest. The diameter of the belt is reduced when the subject is taking such a posture that the upper arm is not in contact with the inner wall of the above-mentioned one end of the receiver. That is, it is preferred that the longitudinal axis line of the upper arm of the subject be kept substantially parallel to the central axis line of the cylindrical arm receiver. However, ordering the subject to change his or her natural posture to the above-mentioned posture may result in forcing the subject to take an unnatural posture, depending upon the conformation of his or her body. This problem is exaggerated in particular for patients or aged persons who are not so free to change their postures. In the latter cases, the accuracy of BP measurements may be lowered.
There is known a BP monitor apparatus which monitors the blood pressure of a living subject. The BP monitor apparatus includes an automatic BP measuring device including an inflatable cuff adapted to be wound around a body portion of the subject. The automatic BP measuring device is iteratively started to measure a BP value or values of the subject. Thus, the BP monitor apparatus carries out BP measurements periodically, i.e., at a prescribed measurement period. However, if the measurement period is prescribed at so short a period to improve the reliability of the BP monitoring, the frequency of pressing of the subject""s body portion with the cuff is increased so that the subject feels a heavy burden. In this situation, there has been proposed a BP monitor apparatus which increases the pressure of an inflatable cuff wound around a body portion of a living subject, up to a prescribed target pressure value, detects a pulse wave as a pressure oscillation produced in the cuff, and continuously estimates a BP value or values based on a magnitude or magnitudes of each of successive heartbeat-synchronous pulses of the pulse wave. Examples of this BP monitor apparatus are disclosed in Non-Examined Japanese Patent Applications No. 61(1986)-103432 and No. 60(1985)-241422. In the latter case, however, if the target pressure is prescribed at as low as possible a value to reduce the burden to the subject, it might be difficult to detect the change of respective amplitudes of successive pulses of the pulse wave corresponding to the change of BP values of the subject. That is, the reliability of the BP monitoring is lowered. The pulse amplitudes detected from the cuff set on people having normal blood pressure change with the cuff pressure so as to have an envelope indicated at solid line in FIG. 29, whereas the pulse amplitudes obtained from people having low blood pressure change with the cuff pressure so as to have an envelope indicated at broken line. Since the amount of change of the pulse amplitudes with respect to the amount of change of the BP values of a subject is more or less small where the pulse amplitudes are obtained at a relatively low cuff pressure such as a value, PK, shown in FIG. 29, the reliability of the BP monitoring at the low cuff pressure PK is insufficiently low.
Furthermore, there is known an automatic BP measuring apparatus which quickly increases the pressure of an inflatable cuff wound around a body portion of a living subject, up to a target pressure value at which the inflated cuff stops the blood flow through the arteries of the body portion, subsequently slowly decreases the cuff pressure at a rate of 2 to 3 mmHg/sec, and measures a BP value or values of the subject during the slow decreasing of the cuff pressure. There are known two BP measuring techniques, i.e., oscillometric method and Korotkoff-sound method. In the oscillometric method, the pressure oscillation produced in the cuff during the slow decreasing of the cuff pressure is detected as a pulse wave, and the systolic and diastolic BP values of the subject are determined based on the change of respective amplitudes of successive heartbeat-synchronous pulses of the pulse wave. In the Korotkoff-sound method, the Korotkoff sounds, i.e., blood-flow sounds produced from the arteries of the body portion during the slow decreasing of the cuff pressure are detected using a microphone, and the systolic and diastolic BP values of the subject are determined based on the two cuff-pressure values at which the first and last Korotkoff sounds are detected, respectively. In these BP measuring methods, the accuracy of measurement of BP values depends on the amount of change of the cuff pressure corresponding to the interval of occurrence of the successive pulses of the pulse wave or the successive Korotkoff sounds. Therefore, for measuring the BP value or values of the subject with accuracy, the automatic BP measuring apparatus carries out the BP measurement while the cuff pressure is slowly decreased. However, since in the prior BP measuring apparatus the cuff pressure is slowly decreased in carrying out the BP measurement, it takes about twenty seconds to obtain the measured BP value or values of the subject. Before this slow cuff-pressure decreasing, no BP value is available to a medical worker such as a doctor. In the case where a doctor should make a quick decision on an emergency patient, or in the case where a target value higher by a prescribed value than the systolic BP value of a subject should be determined while the cuff pressure is quickly increased, so that the cuff pressure is stopped at the thus determined target value, it is required that a BP value of the subject be known, even though it is rough, before a BP measurement is carried out during the slow decreasing of the cuff pressure.
Moreover, there is known the oscillometric BP measuring method in which heartbeat-synchronous signal waves generated from arteries of a living subject are collected while the pressure of an inflatable cuff applied to the arteries is changed, the respective amplitudes of the signal waves are determined to provide a series of wave amplitudes arranged in the order of generation of the signal waves, and a BP value of the subject is determined based on a change of the series of wave amplitudes according to a prescribed software algorithm. An example of the BP measuring method is disclosed in Examined Japanese Patent Application laid open for opposition under Publication No. 2(1990)-25610 assigned to the Assignee of the present U.S. application. The Japanese document discloses a BP measuring apparatus which measures a BP value of a living subject according to the oscillometric BP measuring method, i.e., prescribed software algorithm. The BP measuring apparatus has a display device which displays a series of wave amplitudes in a two-dimensional graph having a first axis indicative of the cuff pressure and a second axis indicative of the wave amplitude. A medical worker such as a doctor can easily recognize, from the distribution of the wave amplitudes with respect to the cuff pressure, the amounts of error of the BP measurement due to external causes such as the physical motion of the subject and the noise produced from peripheral devices. Thus, the doctor can judge whether the conditions of the BP measurement are proper or appropriate. A series of wave amplitudes displayed in the two-dimensional area provided on the display device may define a complex envelope changeable depending upon external factors. There have been employed various smoothening techniques each of which is used to smoothen the envelope of the wave amplitudes obtained in carrying out a BP measurement. The BP measuring method disclosed in Non-Examined Japanese Patent Application laid open for inspection under Publication No. 63(1988)-51837 is one of the smoothening techniques. In this method, an odd number of successive amplitudes are selected from the series of amplitudes, and the amplitude positioned at the center of the selected amplitudes is replaced with the amplitude having the median magnitude. This is the so-called medical filter. By sequentially repeating this median-filter treatment with all the amplitudes by removing the oldest one of the odd number of amplitudes and adding the following amplitude, the envelope of the amplitudes is smoothened. Since a BP measurement is carried out based on the thus smoothened envelope of the amplitudes, the accuracy of measurement of BP values is increased. Although a series of amplitudes are displayed as a two-dimensional graph on the display device, the amplitudes defines only a smoothened envelope wherein the errors of amplitudes due to external factors have been corrected. From a smoothened envelope, a doctor cannot judge whether the conditions of measurement of BP values are proper, unlike a non-smoothened envelope showing the distribution of non-treated xe2x80x9crawxe2x80x9d amplitudes from which the doctor can judge.
It is a first object of the present invention to provide a blood pressure measuring apparatus which enables a patient or a doctor to recognize the time change of the waveforms of pulse waves of the patient and judge whether the patient has a heart disease, when a BP value or values is/are measured on the patient.
The first object has been achieved by the present invention. According to a first aspect of the present invention, there is provided an apparatus for measuring a blood pressure of a living subject, comprising: a blood pressure measuring device which measures a blood pressure value of the subject; a first memory which stores a plurality of blood pressure values measured by the blood pressure measuring device, in an order of measurement of the blood pressure values; a pulse wave detecting device which detects a pulse wave produced from an arterial vessel of the subject in synchronism with heartbeat of the subject while each of the blood pressure values is measured by the blood pressure measuring device; a second memory which stores a waveform of the pulse wave detected by the pulse wave detecting device, in the order, the second memory storing the respective waveforms of the pulse waves each of which is detected by the pulse wave detecting device while a corresponding one of the blood pressure values is measured by the blood pressure measuring device; and an output device which outputs the blood pressure values stored in the first memory, in the order, and a plurality of curves respectively representing the waveforms stored in the second memory, in the order, in a side-by-side relation with each other.
In the BP measuring apparatus in accordance with the first aspect of the invention, the output device outputs the BP values stored in the first memory, in the order of measurement of those BP values, and a plurality of curves representing the waveforms stored in the second memory, in the same order, in a side-by-side relation with each other. The output device may operate in this manner, when the BP apparatus operates for measuring a BP value or values of a living subject such as a patient. Since the BP apparatus is easily used, the patient or a medical worker can easily recognize the time change of the waveforms of the pulse waves of the patient together with the time change of the BP values of the patient. Therefore, the patient or the medical worker can make a diagnosis that the patient may have a heart disease.
In a preferred embodiment in accordance with the first aspect of the invention, the blood pressure measuring device comprises an inflatable cuff adapted to be wound around a body portion of the subject, and the pulse wave detecting device comprises a sensor which detects, as the pulse wave, a pressure oscillation produced in the cuff in synchronism with heartbeat of the subject. In this embodiment, the sensor used as part of the blood pressure measuring device is also used to detect the pulse wave of the patient. Since an exclusive pulse-wave sensor is not needed, the BP apparatus enjoys a simple construction and a low manufacturing cost.
In another embodiment in accordance with the first aspect of the invention, the BP measuring apparatus further comprises amplitude modifying means for modifying an amplitude of each of the waveforms detected by the pulse wave detecting device, so that the waveforms output by the output device have a prescribed amplitude. In this embodiment, the patient or the doctor can easily compare the waveforms of the pulse waves with each other, so that the patient or the doctor can correctly recognize the time change of the waveforms. In this case, the BP measuring apparatus may further comprise wavelength modifying means for modifying a wavelength of the each of the waveforms detected by the pulse wave detecting device, so that the waveforms output by the output device have a prescribed wavelength.
In yet another embodiment in accordance with the first aspect of the invention, the BP measuring apparatus further comprises: evaluating means for evaluating a characteristic of each of the waveforms detected by the pulse wave detecting device, and providing an evaluated value of the each waveform; and a third memory which stores the evaluated value of the each waveform, in the order, wherein the output device outputs the evaluated values stored in the third memory, in the order. In this embodiment, the patient or the doctor can quantitatively figure out the change of the pulse waves, so that the patient or the doctor can more easily recognize the time change of the waveforms of the pulse waves.
In another embodiment in accordance with the first aspect of the invention, the output device comprises means for outputting a first graphical representation indicating the blood pressure values stored in the first memory, and a second graphical representation indicating the evaluated values stored in the third memory, along a common axis indicative of time, and outputting the curves representing the waveforms stored in the second memory, along the common axis. In this embodiment, the BP values, and the evaluated values of the waveforms of the pulse waves are output together with the curves of waveforms along a common xe2x80x9ctimexe2x80x9d axis. The patient or the doctor can more easily recognize the time change of the waveforms.
It is a second object of the present invention to provide an automatic blood pressure measuring apparatus which enables a living body or subject to have a strong visual impression that he or she has a blood pressure abnormality.
The second object has been achieved according to a second aspect of the present invention, which provides an apparatus for measuring a blood pressure of a living subject, comprising: a blood pressure measuring device which measures a blood pressure value of the subject; a first memory which accumulatively stores a plurality of blood pressure values measured by the blood pressure measuring device; a second memory which stores a plurality of pictorial images each of which indicates a corresponding one of a plurality of different evaluations of the blood pressure of the subject; image selecting means for selecting one of the pictorial images which corresponds to a current blood pressure value of the subject measured by the blood pressure measuring device; and an output device which outputs the one pictorial image selected by the image selecting means, together with the blood pressure values stored in the first memory.
In the BP measuring apparatus in accordance with the second aspect of the invention, the output device outputs a pictorial image selected by the image selecting means, together with the BP values stored in the first memory. The pictorial image selected by the image selecting means corresponds to a current BP value of the subject measured by the blood pressure measuring device. Thus, the subject can have a strong visual impression that his or her blood pressure is abnormal, and can keep it in mind for a long time.
In a preferred embodiment in accordance with the second aspect of the invention, the second memory stores a plurality of groups of pictorial images each image of which indicates a corresponding one of a plurality of different evaluations of the blood pressure of the subject, and wherein the apparatus further comprises: a data obtaining device which obtains identification data identifying the subject; and group selecting means for selecting one of the groups of pictorial images which corresponds to the identification data obtained by the data obtaining device, so that the image selecting means selects the one pictorial image from the selected group of pictorial images. In this embodiment, the group selecting means may be adapted to select a group of pictorial images based on the identification data including the personal information of the subject, such as sex, age, and clinical history. Thus, the image selecting means selects a pictorial image which accurately corresponds to a current BP value of the subject measured by the blood pressure measuring device.
In another embodiment in accordance with the second aspect of the invention, the output device comprises a printer which outputs, on a recording sheet, the one pictorial image selected by the image selecting means, together with the blood pressure values stored in the first memory. In this embodiment, the subject can bring the recording sheet on which the selected pictorial image is recorded. Thus, the subject is not required to write down the measured BP values or keep them in mind.
In yet another embodiment in accordance with the second aspect of the invention, the output device comprises means for outputting a graphic representation indicating a time change of the blood pressure values stored in the first memory. In this embodiment, the subject can easily recognize the time change of the BP values.
It is a third object of the present invention to provide an automatic blood pressure measuring apparatus which is easily operable for producing a pictorial image.
The third object has been achieved according to a third aspect of the present invention, which provides an apparatus for measuring a blood pressure of a living subject comprising: a blood pressure measuring device which measures a blood pressure value of the subject; a first memory which accumulatively stores a plurality of blood pressure values measured by the blood pressure measuring device; a second memory which stores at least one pictorial image; an output device which outputs the pictorial image stored in the second memory, together with the blood pressure values stored in the first memory; an image reading device which reads an original image from an original; an editing device which is operable for editing the original image read by the image reading device; and a registering device which registers the image edited by the editing device, by storing the edited image as the pictorial image in the second memory.
In the BP measuring apparatus in accordance with the third aspect of the invention, the image reading device reads an original image from an original, the editing device is operable for editing the original image, and the registering device registers the edited image, by storing it in the second memory. The output device outputs the edited image, i.e., pictorial image together with the BP values stored in the first memory. The pictorial image accompanying the BP values enable the subject to keep the BP values in mind. In addition, the pictorial image is easily prepared and registered in the present BP measuring apparatus.
In a preferred embodiment in accordance with the third aspect of the invention, the second memory stores a plurality of pictorial images each of which is related to a time of measurement of the blood pressure of the subject, and wherein the apparatus further comprises: a clock device which produces a signal indicative of a time when the blood pressure measuring device measures a blood pressure value of the subject; and image selecting means for selecting one of the pictorial images which corresponds to a time of measurement of a current blood pressure value of the subject measured by the blood pressure measuring device, so that the output device outputs the selected one pictorial image together with the blood pressure values stored in the first memory. In this embodiment, the second memory may be adapted to store pictorial images each related to the date and time of measurement of a BP value of the subject, for example, pictorial images representing flowers at four seasons, landscapes at four seasons, etc. The pictorial image accompanying the measured BP values gives a strong visual impression to the subject, so that the subject can keep the BP values in mind.
In another embodiment in accordance with the third aspect of the invention, the second memory stores a plurality of random selectable pictorial images, and wherein the apparatus further comprises: a random value generator which provides, according to a random function, a random value in response to an operation of the blood pressure measuring device; and image selecting means for selecting one of the pictorial images which corresponds to a random value produced by the random value generator, so that the output device outputs the selected one pictorial image together with the blood pressure values stored in the first memory. In this embodiment, in different BP measurements, different pictorial images may be output together with the BP values of the subject. The different pictorial images help the subject to keep the BP values in mind.
It is a fourth object of the present invention to provide an automatic blood pressure measuring apparatus which provides information related to a medicine to be given to a patient, thereby enabling a medical worker to omit the directions for use of the medicine.
The fourth object has been achieved according to a fourth aspect of the present invention, which provides an apparatus for measuring a blood pressure of a living subject, comprising: a blood pressure measuring device which measures a blood pressure value of the subject; a first memory which accumulatively stores a plurality of blood pressure values measured by the blood pressure measuring device; a second memory which stores a plurality of batches of medicine-related information each of which is related to a corresponding one of a plurality of medicines administrable in treating the blood pressure of the subject; an input device which is operable for specifying one of the medicines; and an output device which selects, from the second memory, one of the batches of medicine-related information which corresponds to the one medicine specified by the input device, and outputs the selected batch of medicine-related information, together with the blood pressure values stored in the first memory.
In the BP measuring apparatus in accordance with the fourth aspect of the invention, the output device selects, from the second memory, one of the batches of medicine-related information which corresponds to the one medicine specified by the input device, and outputs the selected batch of medicine-related information, together with the blood pressure values stored in the first memory. In the case where a doctor gives a BP-treating medicine to a patient after having made a diagnosis based on the measured BP values of the patient, the doctor is just required to specify the medicine through the input device, so that the output device outputs, together with the BP values of the patient, the batch of information related to the medicine, the information including the directions for use of the medicine, the objects of administration of the same, and other necessary items. Thus, the doctor is not required to provide any explanation to the patient.
It is a fifth object of the present invention to provide an apparatus for automatically winding an arm belt around an upper arm of a living subject, in measuring a blood pressure of the subject, wherein the apparatus permits the subject to keep his or her natural posture and ensures that the measurement of BP values is carried out with accuracy.
The fifth object has been achieved according to a fifth aspect of the present invention, which provides an apparatus for winding an arm belt including an inflatable bag, around an upper arm of a living subject, in measuring a blood pressure of the subject, a pressurized air being supplied to the bag to inflate the bag and thereby press the upper arm, the apparatus comprising: an arm receiver inside which the arm belt is provided so as to define a substantially cylindrical space into which the upper arm of the subject is inserted from one of opposite ends of the cylindrical space; a positioning device which changes a position of the arm receiver relative to the upper arm of the subject; a detector which detects a misalignment of a central axis line of the cylindrical space of the arm receiver from a longitudinal axis line of the upper arm of the subject; and a control device which controls, based on the misalignment detected by the detector, the positioning device to change the position of the arm receiver relative to the upper arm so that the central axis line of the cylindrical space of the arm receiver is substantially aligned with the longitudinal axis line of the upper arm.
In the arm-belt winding apparatus in accordance with the fifth aspect of the invention, when the subject inserts his or her upper arm into the arm receiver, the detector detects the misalignment of the central axis line of the arm receiver from the longitudinal axis line of the upper arm of the subject, and the control device controls, based on the misalignment detected by the detector, the positioning device to change the position of the arm receiver relative to the upper arm so that the central axis line of the arm receiver is substantially aligned with the longitudinal axis line of the upper arm. Thus, the present apparatus ensures that the upper arm is suitably inserted such that the arteries of the upper arm are not locally or partially pressed by the belt, without requiring the subject to change his or her posture. That is, the present apparatus ensures that the measurement of BP values is effected with accuracy, permitting the subject to keep his or her natural posture.
It is a sixth object of the present invention to provide a BP monitoring apparatus which monitor the blood pressure of a living subject with high reliability and without giving any burden on the subject.
The sixth object has been achieved according to a sixth aspect of the present invention, which provides an apparatus for monitoring a blood pressure of a living subject, comprising: an inflatable cuff adapted to be wound around a body portion of the subject, the cuff being inflated to provide a pressure to press the body portion; a detector which detects a plurality of pulse amplitudes produced in the cuff being inflated to press the body portion; a pressure changing device which increases the pressure of the cuff to a prescribed value lower than a mean blood pressure of the subject, and subsequently decreases the cuff pressure from the prescribed value, in each of a plurality of periodic cycles; rate-of-change determining means for determining, with respect to the cuff pressure, a rate of change of the pulse amplitudes detected by the detector while the cuff pressure is changed by the pressure changing device; and first abnormality judging means for judging, based on the determined rate of change, whether the blood pressure of the subject is abnormal.
In the blood pressure monitoring apparatus in accordance with the sixth aspect of the invention, the rate-of-change determining means determines, with respect to the cuff pressure, a rate of change of the pulse amplitudes detected by the detector while the cuff pressure is changed by the pressure changing device, and the first abnormality judging means judges, based on the determined rate of change, whether the blood pressure of the subject is abnormal. The BP monitoring of the present apparatus is carried out on the discovery that the rate of change of a low-pressure-side portion of the envelope of the pulse amplitudes with respect to the cuff pressure changes as the blood pressure of the subject changes. Therefore, the reliability of the BP monitoring is improved so much. In addition, since the rate of change of the pulse amplitudes is obtained while the cuff pressure is changed in a low-pressure range between atmospheric pressure and the prescribed low pressure, the subject is free of the burden.
In a preferred embodiment in accordance with the sixth aspect of the invention, the monitoring apparatus further comprises a blood pressure measuring device which automatically measures a blood pressure value of the subject in a series of prescribed steps when the first abnormality judging means judges that the blood pressure of the subject is abnormal. In this embodiment, the BP value of the subject just at the time of finding of the blood pressure abnormality is obtained by the blood pressure measuring device. The thus obtained BP value is clinically important, so that a medical worker such as a doctor can make an appropriate treatment on the subject such as a patient.
In another embodiment in accordance with the sixth aspect of the invention, the first abnormality judging means comprises means for judging whether a pulse amplitude detected by the detector while the cuff pressure is changed by the pressure changing device, is smaller than a reference value, the first abnormality judging means judging that the blood pressure of the subject is abnormal, when the pulse amplitude is smaller than the reference value. Since the envelope of pulse amplitudes obtained from people suffering from low blood pressure because of being in a shock state, is more or less flat with respect to the cuff pressure, it is considerably difficult to identify an abnormally low blood pressure based on the rate of change of the pulse amplitudes with respect to the cuff pressure. In this embodiment, however, since a pulse amplitude is compared with a reference value to identify the blood pressure abnormality, the reliability of identification of the subject""s shock state is improved.
In yet another embodiment in accordance with the sixth aspect of the invention, the pressure changing device comprises means for holding the cuff pressure at the prescribed value for a prescribed period of time, and the apparatus further comprises second abnormality judging means for judging, based on a pulse amplitude detected by the detector during the prescribed period, whether the blood pressure of the subject is abnormal. Since the two sorts of abnormality judging means are employed in the present BP monitoring apparatus, the reliability of the BP monitoring is much more improved.
In another embodiment in accordance with the sixth aspect of the invention, the pressure changing device comprises means for increasing and holding the cuff pressure to and at a first prescribed value, and subsequently increasing and holding the cuff pressure to and at a second prescribed value higher than the first prescribed value, and the rate-of-change determining means comprises means for determining, with respect to the cuff pressure, a rate of change of a pulse amplitude detected by the detector when the cuff pressure is held at the second prescribed value from a pulse amplitude detected by the detector when the cuff pressure is held at the first prescribed value. In this embodiment, the rate-of-change determining means determines, with accuracy, the rate of change of a low-pressure-side increasing portion of the envelope of the pulse amplitudes, based on the respective pulse amplitudes detected at the first and second cuff-pressure values. Thus, the reliability of the BP monitoring of the present apparatus is improved. In this case, the rate-of-change determining means may be adapted such that, if at least two successive pulses having substantially the same pulse amplitude are detected while the cuff pressure is held at each of the first and second values, the determining means employs that pulse amplitude in determining the rate of change of the pulse amplitudes. Since in this modified manner xe2x80x9cnoisexe2x80x9d pulses are removed from true pulses, the reliability of the BP monitoring is still more improved.
In another embodiment in accordance with the sixth aspect of the invention, the monitoring apparatus further comprises second abnormality judging means for judging whether the blood pressure of the subject is abnormal, based on a pulse amplitude detected by the detector when the cuff pressure is held at the second prescribed value. In this embodiment, it is not necessary to provide an exclusive cuff-pressure holding period during which to detect a pulse amplitude to be used by the second abnormality judging means for judging whether the subject has blood pressure abnormality.
In another embodiment in accordance with the sixth aspect of the invention, the monitoring apparatus further comprises a blood pressure measuring device which automatically measures a blood pressure value of the subject in a series of prescribed steps when at least one of the first and second abnormality judging means judges that the blood pressure of the subject is abnormal. In this embodiment, when at least one of the first and second abnormality judging means judges that the blood pressure of the subject is abnormal, the blood pressure measuring device automatically measures a blood pressure value of the subject. Thus, the reliability of the BP monitoring is improved so much.
In another embodiment in accordance with the sixth aspect of the invention, the first abnormality judging means comprises means for judging whether the determined rate of change is greater than a reference value, the first abnormality judging means judging that the blood pressure of the subject is abnormal when the determined rate of change is greater than the reference value, and the apparatus further comprises: an input device which is operable for inputting a desired value as the reference value; and changing means for changing, based on the input value as the reference value, the prescribed value to a new value to which the cuff pressure is increased by the pressure changing device. In this embodiment, the cuff pressure applied to the living subject such as a patient is reduced to as low as possible a value.
It is a seventh object of the present invention to provide an automatic blood pressure measuring apparatus which has the function of estimating a BP value of a living subject before an actual BP value of the subject is measured during the decreasing of the cuff pressure.
The seventh object has been achieved by the present invention. According to a seventh aspect of the invention, there is provided an apparatus for automatically measuring a blood pressure of a living subject, comprising: an inflatable cuff adapted to be wound around a body portion of the subject, the cuff being inflated to provide a cuff pressure to press the body portion; a pressure sensor which detects the cuff pressure; a pressure changing device which changes the cuff pressure; a blood pressure measuring device which measures a blood pressure value of the subject by reading the cuff pressure detected by the pressure sensor while the cuff pressure is decreased at a prescribed rate by the pressure changing device; a waveform detector which detects a waveform of a pulse wave produced in the cuff during the decreasing of the cuff pressure, the waveform of the pulse wave being changeable with the cuff pressure; determining means for determining a relationship between (A) evaluated values of a waveform of a pulse wave, (B) pressure values of the cuff, and (C) blood pressure values of the subject, based on (a) an evaluated value of the waveform of the pulse wave detected by the waveform detector, (b) a pressure value of the cuff at a time of detection of the waveform by the waveform detector, and (c) the blood pressure value of the subject measured by the blood pressure measuring device, the relationship being proper to the subject; and estimating means for estimating, according to the determined relationship, a blood pressure value of the subject based on (axe2x80x2) an evaluated value of a waveform of a pulse wave detected by the waveform detector while the cuff pressure is increased before the cuff pressure is decreased at the prescribed rate in measuring an actual blood pressure of the subject and (bxe2x80x2) a pressure value of the cuff at a time of detection of the waveform during the increasing of the cuff pressure.
In the automatic BP measuring apparatus in accordance with the seventh aspect of the invention, the estimating means estimates, according to the determined relationship, a BP value of the subject based on (axe2x80x2) an evaluated value of the waveform of at least one pulse of a pulse wave detected by the waveform detector while the cuff pressure is increased before the cuff pressure is decreased and (bxe2x80x2) a pressure value of the cuff at the time of detection of the waveform during the increasing of the cuff pressure. Thus, the present apparatus quickly gives a doctor an estimated BP value of the subject, even though the estimated value may be some or less rough.
In a preferred embodiment in accordance with the seventh aspect of the present invention, the BP measuring apparatus further comprises evaluating means for evaluating a plurality of characteristics of the waveform of the pulse wave detected by the waveform detector during the decreasing of the cuff pressure, and providing an evaluated value of each of the waveform characteristics, and the determining means determines a plurality of relationships each based on the evaluated value of a corresponding one of the waveform characteristics and the estimating means calculates a plurality of blood pressure values of the subject according to the determined relationships, respectively, and estimates the blood pressure value of the subject based on the calculated blood pressure values. In this embodiment, since the estimated BP value of the subject is provided based on a variety of BP values determined according to a plurality of sorts of relationships, the reliability of the estimated BP value is increased. The waveform characteristics may comprise at least two selected from the pulse amplitude, Amp-b; the maximum slope of the increasing portion of the waveform, SLOPE; the degree of sharpness of the waveform, %MAP; the percentage of the increasing portion of the waveform to the cyclic period thereof, %IPP; and the percentage of the time difference between the primary and secondary peaks of the waveform to the cyclic period thereof, PI (peak index).
In another embodiment in accordance with the seventh aspect of the present invention, the BP measuring apparatus further comprises target pressure determining means for determining, based on the estimated blood pressure value of the subject, a target pressure value to which the cuff pressure is increased, and the pressure changing device starts decreasing the cuff pressure after the cuff pressure is increased to the target pressure. In this embodiment, the cuff pressure is increased up to the target pressure that may be higher by a prescribed value than an estimated systolic BP value of the subject. Therefore, the cuff pressure is by no means increased up to an unnecessarily high pressure relative to the systolic BP value of the subject, or is by no means re-increased to another target pressure higher than the first or initial target pressure when the first target pressure is not sufficiently high. Thus, the burden to the subject is reduced as such.
In another embodiment in accordance with the seventh aspect of the present invention, the BP measuring apparatus further comprises: abnormality identifying means for identifying a blood pressure abnormality of the subject by comparing the estimated blood pressure value of the subject with a reference value; and an output device which outputs, when the blood pressure abnormality of the subject is identified, information indicative of the identification of the blood pressure abnormality of the subject. In this embodiment, the output device informs a doctor of whether the blood pressure the subject is abnormal, at an early stage when the cuff pressure is increased before being decreased. Thus, the doctor can make a quick decision on whether to give a medical treatment to the subject.
According to an eighth aspect of the present invention, there is provided an apparatus for automatically measuring a blood pressure of a living subject, comprising: an inflatable cuff adapted to be wound around a body portion of the subject, the cuff being inflated to provide a cuff pressure to press the body portion; a pressure sensor which detects the cuff pressure; a pressure changing device which changes the cuff pressure; a blood pressure measuring device which measures a blood pressure value of the subject by reading the cuff pressure detected by the pressure sensor while the cuff pressure is decreased at a prescribed rate by the pressure changing device; a waveform detector which detects a waveform of a pulse wave produced in the cuff during the decreasing of the cuff pressure, the waveform of the pulse wave being changeable with the cuff pressure; a memory which stores a pulse amplitude of the pulse wave detected by the waveform detector, and a pressure value of the cuff at a time of detection of the pulse amplitude;
determining means for determining an envelope representing a relationship between (a) a plurality of pulse amplitudes detected by the waveform detector while the cuff pressure is increased before the cuff pressure is decreased at the prescribed rate and (b) a plurality of pressure values of the cuff at respective times of detection of the pulse amplitudes; and estimating means for estimating a blood pressure value of the subject, based on the determined envelope, according to a prescribed relationship.
In the automatic BP measuring apparatus in accordance with the eighth aspect of the invention, the estimating means estimates a BP value of the subject, based on the determined envelope, according to a prescribed relationship between blood pressure and a shape-related characteristic of an envelope. The prescribed relationship is, e.g., such that two cuff-pressure values respectively corresponding to two points on the envelope at which the amplitudes of the envelope significantly largely change, are estimated as the systolic and diastolic BP values of the subject, like the relationship employed in the oscillometric BP determining method. The present apparatus provides a doctor with the estimated BP value of the subject, based on the envelope obtained during the increasing of the cuff pressure before the decreasing of the same. Thus, the doctor quickly obtains an estimated BP value of a patient, even if the estimated value may be some or less rough.
It is an eighth object of the present invention to provide a blood pressure measuring apparatus which determines a blood pressure value of a living subject based on a series of smoothened wave amplitudes and which enables a medical worker to easily judge whether the condition of measurement of BP values is proper or not.
The eight object has been achieved by the present invention. According to a ninth aspect of the invention, there is provided an apparatus for measuring a blood pressure of a living subject, comprising: an inflatable cuff adapted to be wound around a body portion of the subject, the cuff being inflated to provide a cuff pressure to press the body portion; a pressure changing device which changes the cuff pressure; a blood pressure measuring device which (a) obtains a heartbeat-synchronous signal wave generated from arteries of the body portion in synchronism with heartbeat of the subject while the cuff pressure is changed by the pressure changing device, (b) determines respective amplitudes of a plurality of successive pulses of the heartbeat-synchronous signal wave each of which corresponds to one cycle of heartbeat of the subject, and provides, as a first series of determined pulse amplitudes, the determined pulse amplitudes arranged in an order of generation of the corresponding pulses, (c) smoothens the first series of determined pulse amplitudes and thereby provides a second series of smoothened pulse amplitudes, and (d) determines a blood pressure value of the subject based on a change in the second series of smoothened pulse amplitudes; an output device which outputs a two-dimensional representation comprising a number of picture elements; and a control device which controls the output device to output the two-dimensional representation containing the first series of determined pulse amplitudes and the second series of smoothened pulse amplitudes such that one of the first and second series of pulse amplitudes are superimposed on the other series of pulse amplitudes.
In the BP measuring apparatus in accordance with the ninth aspect of the invention, the output device outputs the two-dimensional representation containing the first series of determined pulse amplitudes and the second series of smoothened pulse amplitudes such that one of the first and second series of pulse amplitudes are superimposed on the other series of pulse amplitudes. Therefore, a medical worker such a doctor can visually recognize the differences between the first and second series of pulse amplitudes in the two-dimensional representation. Those differences result from external factors such as the physical motion of the subject or the noise generated from peripheral devices. Based on the total amount of the differences and the respective positions of the differences with respect to the cuff pressure, the doctor can easily judge whether the measured BP value contains a great error due to the external factors, i.e., whether the condition of measurement of the BP value is proper.
According to a tenth aspect of the present invention, there is provided an apparatus for measuring a blood pressure of a living subject, comprising: an inflatable cuff adapted to be wound around a body portion of the subject, the cuff being inflated to provide a cuff pressure to press the body portion; a pressure changing device which changes the cuff pressure; a blood pressure measuring device which (a) obtains a heartbeat-synchronous signal wave generated from arteries of the body portion in synchronism with heartbeat of the subject while the cuff pressure is changed by the pressure changing device, (b) determine respective amplitudes of a plurality of successive pulses of the heartbeat-synchronous signal wave each of which corresponds to one cycle of heartbeat of the subject, and provides, as a first series of determined pulse amplitudes, the determined pulse amplitudes arranged in an order of generation of the corresponding pulses, (c) smoothens the first series of determined pulse amplitudes and thereby provides a second series of smoothened pulse amplitudes, and (d) determines a blood pressure value of the subject based on a change in the second series of smoothened pulse amplitudes; an output device which outputs a degree of propriety of a measurement condition under which the blood pressure value of the subject is determined by the blood pressure measuring device; calculating means for calculating a degree of correction of the second series of smoothened pulse amplitudes from the first series of determined pulse amplitudes, by calculating a ratio of (a) respective differences between (a1) the determined pulse amplitudes corresponding to respective pressure values of the cuff within a prescribed pressure range and (a2) the corresponding smoothened pulse amplitudes, to (b) at least one of the determined pulse amplitudes and the corresponding smoothened pulse amplitudes; and a control device which controls the output device to output the degree of propriety of the measurement condition which corresponds to the degree of correction of the second series of pulse amplitudes calculated by the calculating means.
In the BP measuring apparatus in accordance with the tenth aspect of the invention, the output device outputs the degree of propriety of the measurement condition which corresponds to the degree of correction of the second series of pulse amplitudes calculated by the calculating means. Thus, a medical worker can visually recognize the degree of propriety of the condition of BP measurement. By comparing the degree of correction reflecting the amount of external factors, with a prescribed reference value, the present apparatus may automatically judge whether the measured BP value contains a great error due to the external factors, i.e., whether the condition of measurement of the BP value is proper.